This Core on mutagenesis, expression and cell culture will provide a heavily relied upon service to the center, providing most of the experimental material for Projects I and II and a lesser amount to Projects III and IV. The fundamental role is to generate in vitro mutant versions of CFTR, in most cases expressed in non-epithelial cell lines for the addressing of specific questions regarding the function of the molecule, its localization, or its effect on the cells. In Project I, a high priority question will be the identification of the part of CFTR which participates in the complex with the chaperone, calnexin; in Project II, changes will be made to manipulate specific biophysical properties of the pore through which chloride passes; in Project III, other chloride channels, including ClC1 and P-glycoprotein ('putative channel") will be expressed to evaluate their response to the postulated regulatory molecule I/Cln. Project IV will make less use of these heterologous expression systems but will assess changes in the expression of specific mucins in primary cultures and the tissues from which they are derived.